1. Field of the Invention
The present invention relates generally to arylene sulfide copolymer coating compositions and processes, and more particularly, to low temperature heat curable arylene sulfide copolymer blends, coating compositions including such blends and processes of coating substrates.
2. Description of the Prior Art
Poly(arylene sulfide) resins have properties such as excellent thermal stability and chemical resistance which make the resins useful for coating substrates. Coating-grade poly(phenylene sulfide) resins are generally prepared substantially in accordance with the basic method described in U.S. Pat. No. 3,354,129 issued November 21, 1967, whereby a mixture containing para-dichlorobenzene, sodium hydroxide, a sulfur source such as sodium hydrosulfide and a polar organic reaction medium such as N-methylpyrrolidone is caused to react. The resulting poly(p-phenylene sulfide) resins can be applied to a substrate as a finely divided solid in a slurry and cured by heating in air to form a tough, chemical-resistant coating on the substrate.
In order to form a continuous, smooth and flexible coating on the substrate, it is generally necessary to cure the poly(p-phenylene sulfide) resin at a temperature above about 370.degree. C. Such a high cure temperature has the disadvantages of requiring special heating equipment which increases the cost of the coating procedure, and limiting the types of substrates on which the coating can be applied. That is, some substrate materials are degraded by exposure to temperatures as high as 370.degree. C., and therefore, coatings of poly(p-phenylene sulfide) resin cannot be utilized on such substrates.
Thus, there is a need for coating compositions of arylene sulfide polymers which can be cured at relatively low temperatures whereby special equipment is not required and heat sensitive substrates are not damaged when the coating composition is cured.